The Pentagon on Monday unveiled plans for "disciplined" defense spending for next year but offered up no contingency plans in case Congress fails to prevent sweeping cuts in military spending.

The Defense Department's request of $613 billion for fiscal year 2013 essentially holds spending steady after a decade of gargantuan budgets, and avoids deep reductions while saving money from the withdrawal of US forces out of Iraq and a gradual troop drawdown in Afghanistan.

The Pentagon's base budget would reach $525.4 billion starting in October, slightly down compared to $530.6 billion in the current fiscal year, while war spending would decline to $88.5 billion from $115.1 billion at present.

The figures represent the first drop in the base budget since the beginning of 10 years of steady expansion that followed the attacks of September 11, 2001.

Fiscal pressures have forced military chiefs to scale back projected spending by $487 billion over the next decade, a task they have described as tough but manageable.

But a threat of dramatic defense cuts looms on the political horizon.

If Congress fails to agree by January 2013 on how to slash the deficit, dramatic defense reductions of about $500 billion would be triggered under a law adopted last year.

Defense Secretary Leon Panetta and senior officials warn such cutbacks would be catastrophic and could jeopardize the country's military power.

But the Pentagon has steadfastly insisted it will not draw up any fallback plan in the event of deadlock in Congress.

Analysts say Panetta has calculated that even discussing contingencies could make the deep cuts more likely.

"We are not planning" for the possible automatic cuts, as the administration sees it as a flawed "meat-axe approach," Comptroller Robert Hale, who oversees the Pentagon's budget, told a news conference.

In outlining the department's proposed spending, the Pentagon touted the plan as a careful balancing of priorities underscoring an era of austerity after years of unfettered growth.

"The proposed budget makes more disciplined use of defense dollars to maintain the world's finest military and sustain US global leadership," the department said in a statement.

As part of reductions in weapons programs, the Pentagon said it plans to save $15.1 billion over the next five years by slowing production of the new F-35 fighter jet to allow more time to iron out technical problems.

The new budget attempts to tackle the mushrooming cost of military pay and benefits, which has grown by nearly 90 percent since 2001. The Pentagon proposed increasing health care fees and slowing down pay raises over the next five years, but none of the changes would apply to active duty service members or survivors of deceased troops.

With troop numbers in Afghanistan coming down after a peak of 100,000 in 2010-11, the administration anticipated slashing war spending by 23 percent over the current fiscal year. The reduction included a drop in funds for training and equipping Afghan security forces, from $11.2 billion to $5.7 billion in 2013.

But officials said the administration remained fully committed to building up the Afghan forces, and funding would decline only because Afghan troops now had most of the weapons and gear they required.

The department cited several programs as high priorities, including $3.4 billion for cyber warfare, $3.8 billion for drone aircraft, $8 billion for space "initiatives," $9.7 billion for missile defense and $10.4 billion for special operations forces -- elite troops who have taken on a pivotal role since 9/11.

Critics on the political right have warned that the American military could be seriously weakened by the proposed spending plan, saying too little money is being devoted to high-tech weaponry.

But voices on the left, including some of Obama's fellow Democrats in Congress, argue the defense budget is still bloated and have called for deeper cuts to weapons programs, including less spending on the US nuclear arsenal.

The US military budget far exceeds that of other countries.

China, which has the world's second largest military budget, says it spent 601.1 billion yuan ($91.1 billion) in 2011, though many foreign experts believe the actual figure is higher.